Device and process for touch and proximity detection

Abstract

The invention relates to a device for touch/proximity detection, especially a capacitive switch device, which is designed to set switching states by approaching the switch device or by touching the switch device, in order to perform, for example, switching actions on an instrument. The invention also relates to a switch device, especially a switch device on a capacitive basis, for a cooktop, for operating the cooktop.

The invention claimed is: 
     
       1. A device for touch/proximity detection, comprising
 a detection unit comprising a generator outputting a signal for generating an electric field, 
 an electrode structure having at least one detector electrode and at least one auxiliary electrode arranged at a predetermined distance from the detector electrode, and 
 a first modulator coupled between the at least one detector electrode and the generator and receiving said signal, wherein the first modulator modulates the signal depending on a capacitive coupling of said detector electrode and an approaching object, 
 a second modulator coupled between the at least one auxiliary electrode and the generator and receiving said signal, wherein the second modulator modulates the signal depending on a capacitive coupling of said auxiliary electrode and the approaching object; and 
 wherein the detection unit further comprises a detector for detecting a change of the modulation generated by said first and second modulator. 
 
     
     
       2. The device according to  claim 1 , wherein the detector being configured to detect indicative signals for capacitive couplings between the electrodes and the object, and the areas of the detector electrode and the auxiliary electrode as well as the arrangement of the detector electrode and the auxiliary electrode relative to each other are selected such that in case of an approach of the object to the electrode structure up to a predetermined distance a quotient between a second capacitive coupling between the auxiliary electrode and the object and a first capacitive coupling between the detector electrode and the object is greater than 1. 
     
     
       3. The device according to  claim 1 , wherein the second modulator modulates the signal depending on a capacitive coupling of said auxiliary electrode and an approaching object, wherein the second modulation device is capacitively coupled with the detection unit. 
     
     
       4. The device according to  claim 1 , wherein the detector electrode is substantially circular and the auxiliary electrode is substantially annular and arranged around the detector electrode. 
     
     
       5. The device according to  claim 1 , wherein a shield electrode is arranged between the detector electrode and the auxiliary electrode. 
     
     
       6. The device according to  claim 1 , wherein the auxiliary electrode comprises at least two electrode segments each coupleable with an associated modulation device and each being capacitively coupleable with the detection unit. 
     
     
       7. The device according to  claim 1 , wherein the detector electrode and the auxiliary electrode can be brought into capacitive coupling with each other with a predetermined first coupling capacitance, between the auxiliary electrode and the object a second coupling capacitance being formed that undergoes a change in case of an approach of the object to the auxiliary electrode and/or at a touch of the auxiliary electrode by the object, the first coupling capacitance and the second coupling capacitance forming a total capacitance between the detector electrode and the object. 
     
     
       8. The device according to  claim 1 , wherein the detection unit is configured to detect the total capacitance between the detector electrode and the object. 
     
     
       9. The device according to  claim 1 , wherein the auxiliary electrode being arranged substantially in parallel to and at a predetermined spacing from the detector electrode. 
     
     
       10. The device according to  claim 1 , wherein a touch of the auxiliary electrode by the object causes an abrupt rise in a total capacitance between the detector electrode and the object. 
     
     
       11. The device according to  claim 2 , wherein each of the first and second modulators has one input coupling electrode and wherein a capacitive coupling of the detection means with the first and second modulator is created by said signal which is fed to the input coupling electrodes. 
     
     
       12. The device according to  claim 11 , wherein the first and/or second modulator is supplied with energy with the alternating electric field. 
     
     
       13. The device according to  claim 3 , wherein the first modulator is coupled with the detection unit by a galvanic coupling. 
     
     
       14. The device according to  claim 3 , wherein each of the first and second modulators comprises one oscillation circuit and one frequency divider. 
     
     
       15. The device according to  claim 3 , wherein each of the first and second modulators is adapted to create an amplitude modulation indicative of the respective modulation device and of the electric variable with a predetermined frequency. 
     
     
       16. The device according to  claim 2 , wherein the detection unit comprises:
 an electric circuit for generating an electric field and coupleable to coupling electrodes of the device for touch/proximity detection, and 
 means for evaluating an electric variable by detection of a load change in the electric circuit. 
 
     
     
       17. The device according to  claim 16 , wherein the load change is effected at different frequencies by said first and second modulators, the means for evaluating are operable to detect the load change at different frequencies, the detection unit further comprising means for generating a switching signal. 
     
     
       18. The device according to  claim 17 , further comprising means for frequency analysis, the means for generating a switching signal being configured such that a level change of the switching signal takes place when a direct component caused by the first modulator exceeds or falls below a direct component caused by the second modulator. 
     
     
       19. The device according to  claim 16 , wherein the electric circuit comprises:
 an LC resonant circuit with a signal generating circuit and having a high-quality factor for generating the electric field; and 
 a transmitting electrode connected in parallel to the LC resonant circuit, a capacitance of the transmitting electrode constituting a part of the resonant circuit capacitance, the electric field generated by the LC resonant circuit being emittable by the transmitting electrode. 
 
     
     
       20. The device according to  claim 18 , wherein the direct components of the amplitudes of the separate parts correspond to the capacitive couplings between the electrodes of the device and the object. 
     
     
       21. An operating panel comprising at least one device for touch/proximity detection, the device comprising:
 a detection unit comprising a generator outputting a signal for generating an electric field, 
 an electrode structure having at least one detector electrode and at least one auxiliary electrode arranged at a predetermined distance from the detector electrode, and 
 a first modulator coupled between the at least one detector electrode and said generator and receiving said signal, wherein the first modulator modulates the signal depending on a capacitive coupling of said detector electrode and an approaching object, 
 a second modulator coupled between the at least one auxiliary electrode and said generator and receiving said signal, wherein the second modulator modulates the signal depending on a capacitive coupling of said auxiliary electrode and the approaching object; and
 wherein the detection unit further comprises a detector for detecting a change of the amplitude modulation generated by said first and second modulators, 
 
 wherein the auxiliary electrode is arranged at the user side of the operating panel and the detector electrode at the back side of the operating panel. 
 
     
     
       22. The operating panel according to  claim 21 , wherein an arrangement of the auxiliary electrode and the detector electrode relative to each other is selected such that the detector electrode and the auxiliary electrode form a capacitive coupling with a predetermined coupling capacitance.